Video conferencing apparatus and method for configuring a communication session

ABSTRACT

A method of setting up communication sessions in a telepresence call including a multiple point-to-point connections between at least two telepresence systems, wherein the information required for setting up the communication sessions is embedded in a control protocol message flow establishing a first communication session between the two telepresence systems.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Application No. 61/122,155, filed on Dec. 12, 2008, and NorwegianApplication No. NO 20085194, filed on Dec. 12, 2008. The entirety ofeach is incorporated herein by reference.

FIELD OF THE INVENTION

This disclosure relates to video conferencing systems and telepresence.

BACKGROUND

Conventional videoconferencing systems include a number of end-pointscommunicating real-time video, audio and/or data (often referred to asduo video) streams over and between various networks such as WAN, LANand circuit switched networks.

A number of videoconference systems residing at different sites mayparticipate in the same conference, most often, through one or moreMultipoint Control Units (MCUs) performing switching and mixingfunctions to allow the audiovisual terminals to intercommunicateproperly.

However, representing moving pictures requires bulk information asdigital video typically described by representing each pixel in apicture with 8 bits (1 Byte). Such uncompressed video data results inlarge bit volumes, which is difficult to transfer over conventionalcommunication networks and transmission lines in real time due tolimited bandwidth.

Thus, enabling real time video transmission requires a large extent ofdata compression which may compromise picture quality. The compressionof multimedia data to be transmitted, as well as the decompression ofthe multimedia data to be received, takes place in a processor unitconventionally referred to as a codec.

As videoconferencing involves various recourses and equipmentsimultaneously interoperating at different localizations andcapabilities, there is also a need for the possibility to manage theresources involved both for scheduled and ad hoc videoconferencesthrough a video conference manager tool.

Video conferencing systems provide communication between at least twolocations for allowing a video conference among participants situated ateach location. Conventionally, the video conferencing arrangements areprovided with one or more cameras. The outputs of those cameras aretransmitted along with audio signals to a corresponding plurality ofdisplays at a second location such that the participants at the firstlocation are perceived to be present or face-to-face with participantsat the second location.

Further, the images captured by the plurality of cameras must bearranged and displayed so that they generate a non-overlapping and/orcontiguous field of view, so-called continuous presence. Continuouspresence is a mixed picture created from far-end sites in an MCU. Forexample, in case of a videoconference of five participants, each sitewill receive a picture divided into four quadrants with the picturecaptured from each of the other sites inserted in respective quadrants.

Continuous presence or several displays with only one camera preventsthe feeling of eye-contact among participants in video conferencingsystems. Typically, a camera is placed somewhere above the display atwhich a participant is observing a display of the participant from theremote station. Consequently, the camera captures the participant at anangle above and on the side of the participants viewing level or head.Thus, when an image of that participant is displayed at the remotestation, it appears as if the participant is looking down or to the leftor right. Previous solutions to this problem have required complexoptical systems and methods using, for example, a plurality of lensesand mirrors. The solutions have usually been designed for use when thecamera is capturing an image of a single participant, and they fallshort when simultaneously capturing images of multiple participants.

In addition to the lack of sufficient eye-contact, there are also otherlimitations in conventional videoconferencing limiting the feeling ofbeing in the same room. Continuous presence and small displays alsolimit the size of the displayed participants. Low capturing and displayresolution and highly compressed data also contribute to a reduction ofthe experience of presence. Some solutions have tried to improve this byintroducing so-called telepresence systems requiring dedicated highbandwidth communication lines. However, these solutions are not wellsuited to be connected to a conventional LAN or WLAN, and are notinteroperable with conventional videoconferencing systems.

U.S. 2008/0246834 A1 (U.S. application Ser. No. 12/050,004, filed onMar. 17, 2008) describes a communication system which addresses theseissues, wherein at least two telepresence terminals, each terminalhaving at least one transceiver, are connected by more than one separatepoint-to-point connection between the separate transceivers of each ofthe telepresence terminals. Which transceiver in which endpoints toconnect to each other, are set up when a conference is established,e.g., on a request from a control unit or from a conference manager, amaster site starts transmitting instructions to the other participatingtelepresence systems on how to set up connections between them. Theinstructions are sent to the master transceiver, which in turn relaysthe instructions to the other transceivers in question. The instructionsare typically incorporated in an open field in the message flowspecifying the control protocol of establishing video conference call,such as ITU H.241, H.242 or H.243. Previous instructions schemes havebeen unreliable, and as such there is a need in the art of an improvedmethod and system of establishing telepresence conference calls. U.S.2008/0246834 A1 is incorporated in its entirety herein by reference.

SUMMARY

It is an object to provide an apparatus, system and method overcomingthe above described problems.

In particular, in a first aspect, a method is provided which includessetting up communication sessions in a telepresence call between atleast two telepresence systems (TPs), each TP having at least onetransceiver. The information required for setting up the communicationsessions is embedded in a control protocol message flow establishing afirst communication session between a first transceiver of a first TPamong the at least two TPs and a first transceiver of a second TP amongthe at least two TPs. An apparatus and computer readable mediumincluding computer executable instructions to perform the method arealso provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make this disclosure more readily understandable, thediscussion that follows will refer to the accompanying drawings, inwhich:

FIG. 1 shows an example of an endpoint assembly;

FIG. 2 shows another example of an endpoint assembly;

FIG. 3 shows an exemplary hardware arrangement of an endpoint assemblyor an MCU;

FIG. 4 shows an exemplary telepresence apparatus;

FIG. 5 shows an exemplary message flow between a first telepresencesystem and a second telepresence system; and

FIG. 6 shows a state diagram for a method.

DETAILED DESCRIPTION

In the following, aspects of the claimed invention are described withreference to a preferred embodiment, and by referring to theaccompanying drawings. However, people skilled in the art will realizeother applications and modifications within the scope of the inventionas defined in the enclosed independent claims.

Described herein is a novel system for providing realistic presence ofparticipants, or telepresence, in a videoconference by means of standardbased communication. An exemplary endpoint 100 compliant with thissystem is shown in FIG. 1, and includes at least one codec and onecamera 102 for each display 104. The displays are preferablylarge-scaled flat screens placed side by side with the camerasrespectively placed on top of the displays.

There is preferably also an additional display 106, e.g., placed belowthe other displays being reserved for data input, such as presentationsand shared applications or for communicating with regularvideoconferencing endpoints usually having only one camera anddisplaying several sites in the same display. Alternatively, theadditional display 106 is replaced by several table mounted displays asshown in FIG. 2.

There is preferably also a control unit installed in an endpointaccording to the present invention. The control unit has a userinterface, e.g., with a pressure or touch sensitive screen (e.g.,additional display 106 shown in FIG. 2), providing the user access toinitiate calls in addition to all other functions and adjusting allsettings that the system is capable of providing. In other words, in apreferred aspect, the table mounted additional display 106 is touchsensitive and serves both as a display screen and a control interfacefor the control unit. The control unit is also able to receive andexecute commands from a conference manager tool, such as setting upscheduled conferences etc. The control unit is in turn connected to theother parts of the endpoint through a master device that represents thesystem as a whole. The master device could be a part of the controlunit, or it could be one of the codecs. The master device would also bethe only device registered with a conference manager.

Accordingly, telepresence in this context means a videoconferencebetween videoconferencing endpoints, where at least one of the endpointshas at least two displays, and at least one codec and camera for each ofthe displays.

A telepresence compliant endpoint as described above will from now on bedescribed as a telepresence system. As readily understandable for aperson skilled in the art, a telepresence compliant endpoint might bereplaced by a telepresence compliant Multipoint Control Unit (MCU), alsoknown as a telepresence server.

Generally, as shown in FIG. 3, an exemplary MCU 10 includes a CPU 12,which processes data and instructions stored in memory 14 and/or ROM 16.The CPU 12 also processes information stored on the disk 18 or CD-ROM 20through a disk controller 2. The exemplary CPU 12 may be an IntelPentium-based processor from Intel of America. Of course, otherprocessor and hardware vendors and types are known in the art such asFreescale ColdFire, i.MX and ARM processors from Freescale Corporationof America. Thus, instructions corresponding to the processes describedherein and in accordance with exemplary aspects of this disclosure arestored on any one of the memory 14, ROM 16, disk 18, or CD-ROM ROM 20.The memory 14 may include random access memory (RAM), flash memory,EEPROM memory, or the like, while the ROM 16 is read-only memory, suchas PROMs; the disk 18 is a hard disk drive, a solid state drive, or acombination thereof; and the CD-ROM drive 20 preferably includes DVDfunctionality.

In some aspects, the MCU 10 includes an application-specific processor(ASP) 22, which is preferably a programmable processor. The ASP 22 isconfigured to perform video compression and/or decompression. Forexample, the ASP 22 is a MPEG-based codec. Alternatively, the MCU 10includes computer-readable instructions which enable the CPU 12 tocompress and/or decompress video.

The MCU 10 also preferably includes a network interface 23, such as a anIEEE 802.x compliant network controller, for interfacing with the MCU 10via a network 24 or the Internet; a display controller 26 forinterfacing with displays 28, such as an LCD or plasma-based display;and cameras 30 and microphones 32 interfaced through an I/O interface 34to a BUS 36. As discussed above, at least one ASP 22 and camera 30 isprovided for each of displays 28.

In some aspects, the MCU 10 also includes a keyboard 38 and a pointingdevice 39 interfaced through the I/O interface 34. A description of thegeneral features and functionality of the aforementioned components isomitted for brevity as these features are well known.

The exemplary MCU 10 shown in FIG. 3 is therefore a hardware platform ofa computing device. Computer-readable instructions can be stored on anyone of the aforementioned disk drives or memory devices, including thedisk 18 and the ROM 16. Computer readable-instructions may also beprovided as a utility application, background daemon, or component of anoperating system, or combination thereof, executing in conjunction withCPU 12 and an operating system such as UNIX, Solaris, LINUX and othersystems known to those skilled in the art. Further, it should beappreciated the structural hardware relationships depicted in FIG. 3 canbe alternatively arranged as one skilled in the art will readilyappreciate.

For example, as shown in FIG. 4, a telepresence apparatus 40 is shown toinclude components and a configuration similar to the aforementioned MCU10 shown in FIG. 3. The telepresence apparatus 40, however, shows eachof displays 28 and respective camera(s) 30 and microphones 32 connectedto a respective codec 40, which is a device for encoding and decoding(compressing/decompressing) audio and visual data. The codecs 40 arethen interconnected to the BUS 36 and operation thereof is similar tothe MCU 10 shown in FIG. 3.

It should be appreciated the codec(s) 40 preferably includes circuitryand computer readable instructions to convert audio data from themicrophone(s) 32 and video data from the camera(s) 30 to compressedaudio and video data, including data compliant with an MPEG protocol,for transmission through the network 24. One skilled in the art shouldappreciate other protocols can be implemented.

Additionally, the codec(s) 40 also preferably decompress or de-convertdata received form the network 24 to be rendered on the display(s) 28.To this effect, the display(s) 28 also preferably include speakers (notshown) for rendering audio signals which have been decompressed by thecodec(s) 42. However, it should be appreciated external speakers andamplification systems (not shown) could be used without detracting fromthe scope of this disclosure.

A conference between telepresence systems is arranged by setting upsite-to-site connections between respective codecs of the endpoints,even if the conference is a multi-site conference. Which codecs in whichendpoints to connect to each other, are selected to optimize the feelingof presence for the participants in the conference. As an example, whenthe codec associated with the right camera and the right screen of siteA in a conference is directly connected in a video conference link tothe codec associated with the left camera and the left screen of site B,the participants of site A will experience that the participants of siteB turn to them when the participants of site B look at the left screenwhere the participants of site A are displayed. Examples on how thiswill effect the selection of connection paths in different conferenceconstellations are discussed further below.

According to one aspect, when a conference is established, the onetelepresence system initiating the conference is selected as the mastersite. The master site controls the other telepresence systems in theconference keeping track of status, controlling the establishment of theconference and rearranging the communication links when a telepresencesystem joins or leaves during the conference.

When a conference is to be established, e.g., on a request from thecontrol unit or from a conference manager, a first call is establishedfrom a first master device of a first telepresence system to a secondmaster device of a second telepresence system. Within the first call themaster device and the second master device exchange information, such asthe addresses of the other devices, needed to setting up thesite-to-site connections between respective codecs of the telepresencesystems.

The information are preferably incorporated in an open field in themessage flow specifying the control protocol of establishing videoconference call, in particular the vendor specific messages of the ITUH.245 protocol.

An exemplary message flow according to a method of this disclosure isshown in FIG. 5, wherein a first telepresence system (TP1) is initiatinga telepresence call to a second telepresence system (TP2). The firststep of the telepresence call (not shown) is to establish a first H.323call between the master device of TP1 and TP2. When the first H.323 callis established, a first H.245 channel is also established, eitherdirectly or proxied via at least one gatekeeper, between the respectivemaster device of TP1 and TP2. In step 51 the master devices performs aMaster/Slave determination, and in step 52 the master devices exchangesthe capability sets of the master devices. After steps 51 and 52 arecompleted, it is possible to transmit vendor specific messages using theH.245 protocol.

In step 53, the master device of TP1 starts transmitting a firstinitiation message, or hello message, identifying itself as atelepresence system, to the master device of TP2. The master device ofTP2, after receiving the first initiation message from TP1, transmits asecond initiation message also identifying itself as a telepresencesystem to TP1. In addition to the value indicating a telepresence systemthe initiation message also comprise a determination number and theversion of the protocol being used. The determination number will bedescribed further below with reference to step 54, Master/Slavenegotiation. In addition, the initiation message can preferably alsoinclude the number of screens in the telepresence system.

The master device initiating the telepresence call, i.e. TP1, selects adetermination number in a first range, the device receiving theinitiation message then selects a determination number in a secondrange, wherein the second range comprise numbers of lower values thanthe first range. Preferably the first range is <32768-66635>, and thesecond range is <0-32767>. The telepresence system with the highestvalue is determined to be the master, and accordingly the telepresencesystem with the lowest value is the slave. In step 54, TP1 transmits afirst acknowledgement (ACK) message to TP2 confirming that TP1 is themaster. After receiving the first ACK message, TP2 transmits a negativeACK message to TP1 confirming that TP2 is not the master.

In step 55, the master device of TP1 transmits a first SiteInfo messageto the master device of TP2. After receiving the first SiteInfo message,the master device of TP2 transmits a second SiteInfo message to themaster device of TP1. The SiteInfo message comprises the name of thesystem, the type of the system and the number of any additional devices,or telepresence sockets, which is to be connected.

In step 56, the master device of TP1 transmits a first number ofTPSocket-messages to the master device of TP2, the number ofTPSocket-messages corresponding to the number of telepresence sockets inTP1. After receiving the first number of TPSocket-messages, the masterdevice of TP2 transmits a second number of TPSocket-messages to themaster device of TP1, the number of TPSocket-messages corresponding tothe number of telepresence sockets in TP2. The TPSocket-messagecomprises the position of a socket relative to the position of thecorresponding master device, and the number to be called to reach thesocket.

In step 57, the telepresence sockets (TPSockets) of TP1 establishcommunication sessions with the TPSockets of TP2, by using normal H.323procedures.

In another exemplary embodiment, the message flow also includes messagesto send or request modes of operations of the telepresence conference.Some exemplary modes of operation are described below.

In yet another exemplary embodiment, the message flow also includesmessages to invite more sites into the conference.

According to an exemplary aspect, the messages are sent using thefollowing format:

prefix, command: key₁=‘value₁’ . . . key_(n)=‘value_(n)’

prefix, e.g. TTPP, is preferably used to identify the protocol. However,as readily understandable by a person skilled in the art, prefix can beomitted if not required in a specific application without detractingfrom the scope of this disclosure. Exemplary commands, or messageidentifiers, and their associated keys and values are described below.

The initiation message described above in relation with step 53 isidentified with Experia. The Experia message indentifies thetransmitting system as a telepresence system. The Experia message alsocontains at least two key values: determinationNumber and Version. ThedeterminationNumber value is a number within a first or a second rangeof numbers, wherein the second range includes numbers of lower valuesthan the first range. The telepresence system initiating a call willassign itself as master by choosing a number from the first range.Accordingly, the receiving telepresence system chooses a number from thesecond range when transmitting the Experia message. Preferably the firstrange is <32768-66635>, and the second range is <0-32767>. The Versionvalue is the version of the protocol. Preferably the Experia messagealso contains a Screen-value that identifies the number of screens ofthe system transmitting the message. An exemplary Experia message isshown below:

TTPP, Experia: determinationNumber=66635 Version=1 Screens=3

The acknowledgement message described in relation with step 54 isidentified with ExperiaAck. The ExperiaAck message has one key value:iAmMaster. The iAmMaster value is a Boolean telling the status of themaster/slave negotiation as described above. A system with adetermination number in the first range transmits a “True” value, whilea system with a determination number in the second range transmits a“False” value. An exemplary ExperiaAck message is shown below:

TTPP, ExperiaAck: iAmMaster=true

The SiteInfo message described in relation with step 55 is identifiedwith SiteInfo. The SiteInfo message has three key values: Name, Type andtpSockets. The Name value is the name of the system transmitting themessage, and can be any chosen name. The Type value identifies what typeof system is transmitting the message. The Type values are predefinedvalues for known telepresence compatible systems, e.g. TANDBERGExperiaT3identifies a TANDBERG T3 telepresence endpoint and CodianTPS identifiesa TANDBERG Codian Telepresence server. The tpSockets value gives thenumber of any additional devices, or telepresence sockets, to beconnected for each telepresence system. An exemplary SiteInfo messagefor a three screen TANDBERG T3 telepresence system is shown below:

TTPP, SiteInfo: Type=TANDBERGExperiaT3 name=A, tpSockets=2

The TP-Socket messages described above in relation with step 56 isidentified with TPSocket. The TPSocket message has at least three keyvalues: xPos, yPos and number. The number value is the number the masterdevice will be calling to reach the telepresence socket. Preferably, theTPSocket message also includes a protocol value identifying the relevantcommunication session protocol, default value being H.323. The xPos andyPos values gives the respective horizontal and vertical position of thetelepresence socket in relation to the centre socket, 0 is the centreposition. Exemplary TPSocket messages for a three screen telepresencesystem where all screens are in the same horizontal plane, is shownbelow:

TTPP, TPSocket: xPos=−1 yPos=0 number=ALeft@tandberg.com

TTPP, TPSocket: xPos=1 yPos=0 number=ARight@tandberg.com

In another aspect according to this disclosure, the telepresence systemsselect a mode of operation from a predefined set of camera presets, by atransmitting a Conference message. The Conference message is preferablytransmitted as a part of the site info exchange in step 55. TheConference message is transmitted from the site that owns theconference. The conference owner can be different from the master of theconference. The conference owner is the site that is the master of amultisite conference, i.e. a telepresence server will own the conferenceif multiple telepresence systems is connected to the telepresenceserver. Similarly, a TANDBERG T3 telepresence system will own theconference if multiple endpoints are connected to the T3 system. Whenthe call is set up, the other endpoints or telepresence systems mayrequest the conference owner to change the camera preset by transmittinga CameraPresetRequest message to the conference owner. If the conferenceowner decides to follow the request, the conference owner replays bytransmitting a Conference message. The Conference message and theCameraPresetRequest message both have one key value, namelycameraPreset. The cameraPreset values are predefined camera presetvalues, e.g. p2p2p (Point to point, two person zoom), ot4p (One table,four person zoom), ot2p (One table, two person zoom), p2p3p (Point topoint, three person zoom) and ot6p (One table, six person zoom). Anexemplary Conference message is shown below:

TTPP, Conference: cameraPreset=ot4p

In yet another aspect according to the present invention, the masterdevice invites additional sites during an ongoing telepresenceconference, by transmitting an Invite message. Invite message have twokey values: number and protocol. The number value is the number themaster device will be calling to reach the invited site to be invited.The protocol value is identifying the relevant communication sessionprotocol, e.g. SIP or H.323, used for this call by the master device.The receiving master device will respond by transmitting an InviteResultmessage, the Invitemessage having one key value: status. If the inviteis successful the status value is OK, on the other hand if the invite isnot successful the status value is Error followed by an correspondingerror message. An exemplary invite message exchange is show below:

TTPP, Invite: number=newsite@domain.com protocol=sip

TTPP, InviteResult: status=Error errorMessage

As described above, and shown in FIG. 6, the first step of a methodaccording to this disclosure is an initiation step, or a handshakestate, step 61. During the handshake state the master device of a firsttelepresence system transmits a first message, identifying the firsttelepresence system as a telepresence system, to a master device of asecond telepresence system. On receiving the first message, the masterdevice of the second telepresence system transmits a second message, thesecond message identifying the second telepresence system as atelepresence system. The first and second messages respectively alsoinclude additional information about the respective telepresence system,such as a determination number, the version of a protocol and the numberof screens of the system. The master device initiating the telepresencecall selects a determination number in a first range, the devicereceiving the initiation message then select a determination number in asecond range, wherein the second range comprise numbers of lower valuesthan the first range. Preferably the first range is <32768-66635>, andthe second range is <0-32767>.

In the Master/Slave Negotiation state, step 62, the master devices ofthe telepresence systems determine which of the two telepresence systemsshould be the master of the call between the two telepresence systems.The telepresence system with the highest value is determined to be themaster, and accordingly the telepresence system with the lowest value isthe slave. The first master device transmits a first acknowledgementmessage to the second master device confirming that the firsttelepresence system is the master of the call. After receiving the firstacknowledgement message, the second master device transmits a negativeacknowledgement message to the first master device confirming that thesecond telepresence system is not the master.

In the SiteInfo Exchange state, step 63, each of the telepresencesystems transmits a message to the other telepresence system comprisingthe name of the telepresence system, the type of telepresence system,and the number of additional devices to connect, or tpSockets, to setupthe telepresence call. Preferably, during the SiteInfo Exchange statethe telepresence systems select a mode of operation from a predefinedset of camera presets, by a transmitting a Conference message asdescribed above.

In the TPSocket Exchange state, step 64, each of the telepresencesystems transmits a TPSocket message for each of the tpsockets availablein the telepresence system. The TPSocket message includes at least thehorizontal and vertical position of the tpsocket in relation to themaster device of the system, and the number or address to be called toconnect to the tpsocket. Each telepresence systems checks that aTPSocket message is received for the number of tpSockets received in theSiteInfo message, then the method proceeds to Initialise Call state.

In the Initialize Call state, step 65, the master telepresence systemdials the tpSockets as specified in the TPSocket messages. The tpSocketsreceiving a call answer from an expected call, i.e. a call from a socketidentified in one of the TPSocket messages, and rejects calls from anyother callers. Then, a user of the system can preferably request a newcamera preset by transmitting a camera preset request message asdisclosed above.

After the Initialize Call state, step 65, the method proceeds to theMonitor Call state, step 66. The master device of the mastertelepresence system in the call monitors the different tpSockets in thecall and keeps track of the status of the conference and the differentconnections, then being able to re-establish or rearrange theconnections if necessary. When the call controlling the telepresencecall, i.e. the initial call between the master devices of the twotelepresence systems, is dropped, all other tpSockets calls will bedropped and the telepresence conferece is ended, i.e. step 67. On theother hand, when one of the other tpSocket calls is dropped, the masterdevice re-establishes the call.

Moreover, any processes, descriptions or blocks in flow charts should beunderstood as representing modules, segments, portions of code whichinclude one or more executable instructions for implementing specificlogical functions or steps in the process, and alternate implementationsare included within the scope of the exemplary embodiment of the presentinvention in which functions may be executed out of order from thatshown or discussed, including substantially concurrently or in reverseorder, depending upon the functionality involved, as would be understoodby those skilled in the art.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A method of setting up communication sessions in a telepresence callbetween at least a first and a second telepresence (TP) system, each TPsystem having at least one transceiver, wherein information required forsetting up the communication sessions is embedded in a control protocolmessage flow establishing a first communication session between a firsttransceiver of the first TP system and a first transceiver of the secondTP system, the method comprising: transmitting a first message from thefirst transceiver of the first TP system to the first transceiver of thesecond TP system, the first message defining a TP call; transmitting asecond message from the first transceiver of the first TP to the firsttransceiver of the second TP system, the second message defining one ofthe TPs as a master TP system of the TP call; transmitting a thirdmessage from the first transceiver of the first TP system to the firsttransceiver of the second TP system and a fourth message from the firsttransceiver of the second TP system to the first transceiver of thefirst TP system wherein the third and the fourth messages respectivelyinclude the number of additional transceivers (sockets), addresses ofthe sockets, and positions of the sockets relative to the firsttransceiver of the TP from which it is transmitted; and initializing thetelepresence call from the master TP system, including instructing thesockets associated with the master TP system to set up point-to-pointcommunication sessions with corresponding sockets associated with otherTP systems, which are not defined as master TP system.
 2. The methodaccording to claim 1, wherein the first message includes a first numberselected by the first transceiver of the first TP system from a firstrange of numbers, the method further comprising: transmitting a fifthmessage from the first transceiver of the second TP system to the firsttransceiver of the first TP system, the fifth message including a secondnumber selected by the first transceiver of the second TP system from asecond range of numbers, the second range of numbers including numbershaving values lower than the first range of numbers, and defining the TPsystem transmitting the highest number as the master TP system of the TPcall.
 3. The method according to claim 1, wherein the message definingone of the TP systems as the master TP of the TP call includes anacknowledgement (ACK) message, the ACK message being either positive ifthe transmitting TP system is the master TP system of the TP call, ornegative if the transmitting TP system is not the master TP system ofthe TP call.
 4. The method according to claim 1, wherein the positionsof the sockets include relative vertical positions and relativehorizontal positions.
 5. The method according to claim 1, the methodfurther comprising: selecting a mode of operation of the TP call from apredefined set of camera presets; and transmitting a first TP callconfiguration message from the master TP system to the other TP systemsin the TP call to change the camera preset of the other TP systems. 6.The method according to claim 5, the method further comprising:transmitting a first TP call re-configuration request message from oneof the other TP systems to the master TP system, the re-configurationrequest message requesting a change of camera presets; determiningwhether to change the camera presets, by the master TP system uponreceiving the re-configuration request message; and transmitting a callconfiguration message from the master TP system to the other TP systemsin the TP call to change the camera preset of the other TP systems whenthe master TP determines to change the camera presets in response there-configuration request message.
 7. The method according to claim 1,wherein the third and the fourth messages further include a type of TPsystem which is transmitting the respective message.
 8. The methodaccording to claim 7, wherein at least one of the TP systems is atelepresence compliant multipoint control unit or telepresence server.9. The method according to claim 1, wherein at least one of thetransceivers is a codec.
 10. The method according to claim 1, whereinthe control protocol is ITU H.245.
 11. A computer-readable mediumincluding computer-executable instructions, which are executed by aprocessor to perform a method of setting up communication sessions in atelepresence call between at least a first and a second telepresence(TP) system, each TP system having at least one transceiver, whereininformation required for setting up the communication sessions isembedded in a control protocol message flow establishing a firstcommunication session between a first transceiver of the first TP systemand a first transceiver of the second TP system, the method comprising:transmitting a first message from the first transceiver of the first TPsystem to the first transceiver of the second TP system, the firstmessage defining a TP call; transmitting a second message from the firsttransceiver of the first TP to the first transceiver of the second TPsystem, the second message defining one of the TPs as a master TP systemof the TP call; transmitting a third message from the first transceiverof the first TP system to the first transceiver of the second TP systemand a fourth message from the first transceiver of the second TP systemto the first transceiver of the first TP system wherein the third andthe fourth messages respectively include the number of additionaltransceivers (sockets), addresses of the sockets, and positions of thesockets relative to the first transceiver of the TP from which it istransmitted; and initializing the telepresence call from the master TPsystem, including instructing the sockets associated with the master TPsystem to set up point-to-point communication sessions withcorresponding sockets associated with other TP systems, which are notdefined as master TP system.
 12. A telepresence (TP) apparatus,comprising: a local transceiver; a transmitting unit configured toinitiate a control protocol message flow establishing a communicationsession between the local transceiver and a remote transceiver of aremote TP apparatus, including transmitting a first message from thelocal transceiver to the remote transceiver, the first message defininga TP call; and a receiving unit configured to receive a second messagefrom the remote transceiver, the second message defining either the TPapparatus or the remote TP apparatus as a master TP apparatus of the TPcall, the transmitting unit transmitting a third message from the localtransceiver to the remote transceiver, and the receiving unit receivinga fourth message from the remote transceiver to the local, wherein thethird and the fourth message respectively include a number of additionaltransceivers (sockets) included in the TP apparatus and the remote TPapparatus, addresses of the sockets, and positions of the socketsrelative to, respectively, the local transceiver and the remotetransceiver, and the TP call is initialized from the master TP apparatusby instructing sockets of the master TP apparatus to set uppoint-to-point communication sessions with corresponding socketsassociated with the non-master TP apparatus.